Has a cow got metal in its body?

Not in its body but in its "hardware stomach" the reticulum. In short, yes. Hardware disease can result with metal in the reticulum; Hardware disease happens when a sharp foreign object such as wire or a nail penetrates the gut lining, resulting in infection as the bacteria from the digestive tract gets into this wound in the gut. The only way to prevent this is to orally insert a strong magnet into the cow's stomach to collect the metal that has collected there and keep the metal away from the stomach lining. The magnet is in the stomach throughout the cow's life.

To prevent any hardware disease or any cattle swallowing any pieces of metal it is best to go through the pasture on walks and pick up any nails, pieces of wire, or any other scrap of metal that the animals could swallow. Purchasing hay with no metal in it helps too.